C# DataGridView/DataSet/MySql problem

I've got a problem with my project... in short I've got a mysql db bond through a DataSet and BindingSource - if I'm editing like a user the gridview then all changes are commited to the db no problem...
But I need the user to responsibly change foreign keys - what I have done is: if the user doubleclicks on a foreign key cell a new form pops up with possible values, I can change the cell value to the new foreign ID by:

then the value sets in the datagridview but then the update does not save it into the database... the gridview is bound to my bindingsource/dataset so I would think the changes should be flagged and update when called... but maybe I should try to change the dataset directly?